It seems like green juice has become synonymous with health. And if there were ever a sign of an exploding industry, it would have to be the fact that the number of pretty little shops selling nothing but beautifully-colored juices is starting to rival the crazy number of cupcake places in NYC. And while I love a concoction of kale, apple, lemon, and ginger at The Butcher's Daughter, whenever my patients ask about juices, I tell them to avoid them.

I realize this might sound radical, and that the juice industry is probably already forming an angry mob outside my door. I am an integrative doctor, and I know many of my peers often prescribe shakes and juices. Often the rationale for shakes is that many people have what is called leaky gut, meaning their intestines have been damaged over time by a diet of chemicals, processed food, and pharmaceutical drugs, their digestive systems aren’t functioning well, and they will won’t absorb whole foods properly. The drinks are therefore a delivery vehicle for supplements and nutraceuticals, because in liquid form they are more easily and quickly digested, and therefore will be more fully absorbed into the bloodstream.

This may be true, and helpful when prescribed to replete a specific nutrient in people with real absorption problems, but there are a lot of downsides to a liquid diet—even if only for one meal a day—and for the following reasons I encourage my patients to make juices a treat, never a staple.

Here are five reasons NOT to make juices a routine part of your diet:

1. Juices leave you hungry.

Solids take almost twice as long as liquids to leave your stomach, meaning if you’re having a drink for a meal, you’ll be leaving your belly hurting for something to chew on. Especially for people trying to lose weight, this can end up meaning eating more over the course of the day.

2. Fat is back!

Don’t go back to the terrible, fat-free 80s. Juices generally don’t contain much (if any) fat or protein, both of which stimulate your brain to quiet hunger pangs when they reach your small intestine. This is another reason you won’t be satiated as long from a juice.

3. Constipation!

You need fiber for your gut to move and not get stuck. I once had a patient who had been put on a liquid diet in the hospital after surgery and had gotten confused after discharge and never stopped putting all his meals in a blender. No laxative was strong enough for him. You need fiber to induce proper peristalsis (the waves of contraction of your intestinal muscles that move food along). Juicing pulverizes all that fiber, rendering it useless.

4. You'll miss out on good germs.

Fermentation is the key to health and fermentation happens in the large intestine thanks to plant fiber and the helpful bacteria that like to eat it. You can take all the probiotics you want, but if you don’t give the bugs in your colon the complex carbs and fermentable plant fibers they like to munch on, you miss out on the golden byproduct of bacterial digestion: the short-chain fatty acids that nourish and protect the gut barrier and reduce inflammation.

5. You should detox more than your bloodstream.

In Ayurveda, Ama, or toxic residue, builds up in the tissues as a result of eating unhealthy foods or foods you don’t digest well (like eating bread if you have celiac disease), consuming drugs and alcohol, and stress. Blood is one kind of tissue, but don’t forget about connective tissues like ligaments and tendons, and bones, muscles, nerves and fat.

These tissues can build up Ama, too. Many people use juicing to detox, but while a one-day juice fast might kick-start your kidneys to clean out your plasma, a longer term, healthy detox that includes eating whole, fibrous foods like fruits, vegetables and whole grains like quinoa and farro, will stimulate your gut to keep moving and pull deeply embedded toxins out with it. This kind of detox—for a week or even a month—will leave you clean to the bones without starving and whacking out your metabolism.

My motto is eat real whole food, and don’t drink your calories. You don’t need fancy drinks to be healthy. Just water and sometimes medicinal teas. The occasional green juice is gravy.

Robin Berzin, M.D.

Doctor & Founder Of Parsley Health

Robin Berzin MD is a functional medicine physician and the founder of Parsley Health. Her mission is to make functional medicine affordable and modern, so that more people can access this holistic, root-cause approach to health.
A Summa Cum Laude graduate of the University of Pennsylvania, Robin went to medical school at Columbia University and later trained in Internal Medicine at Mount Sinai Hospital. She is also a certified yoga instructor and a meditation teacher, and has formally studied Ayurveda. Robin writes for a number of leading wellness sites, and speaks regularly for organizations including the Clinton Foundation, Health 2.0, Summit, and the Functional Forum, on how we can reinvent health care.
She's also an mindbodygreen courses instructor, teaching her Stress Solution program designed to help you tune down the stress in your life and tune up your energy and happiness.